1. Field of the Invention
The present invention relates to a cassette for storing a stimulable phosphor sheet and used for photographing a radiation image. More specifically, the present invention relates to a cassette comprising means for erasing radiation energy remaining in a stimulable phosphor sheet stored therein.
The present invention also relates to a radiation image photographing apparatus for photographing (recording) a radiation image in the stimulable phosphor sheet stored in the cassette.
Furthermore, the present invention relates to a photographing information registration apparatus for registering photographing information regarding the stimulable phosphor sheet stored in the cassette.
Moreover, the present invention also relates to a radiation image information reading apparatus for reading radiation image information recorded in the stimulable phosphor sheet stored in the cassette.
2. Description of the Related Art
There has been known stimulable phosphor storing a portion of energy of radiation irradiated thereon and emitting phosphorescent light in accordance with the stored radiation energy upon exposure to an excitation light such as visible light and a laser beam. Consequently, radiation image recording/reproducing systems using stimulable phosphor sheets having the stimulable phosphor on substrates thereof have been in wide use.
A radiation image recording reproducing system records radiation image information of a subject such as a human body in a stimulable phosphor sheet by irradiating radiation that has passed through the subject on the sheet. Thereafter, the stimulable phosphor sheet is scanned two-dimensionally with an excitation light such as a laser beam to cause the sheet to emit phosphorescent light from an area where the excitation light is irradiated, and the phosphorescent light is read by photoelectric reading means. In this manner, an image signal representing the radiation image information is obtained by the radiation image recording/reproducing system (see Japanese Unexamined Patent Publication Nos. 55(1980)-12429, 55(1980)-116340, and 56(1981)-104645, for example).
The image signal obtained by the system in the above manner is subjected to image processing such as tone processing and frequency processing appropriate for observing a radiation image represented by the image signal, and the image is reproduced as a visible image on a film or displayed on a CRT display device for diagnosis.
The stimulable phosphor sheet can be used repeatedly for recording radiation image information again if an erasing light for releasing radiation energy remaining in the sheet is irradiated on the sheet after reading. However, even if the erasing process described above is carried out after reading, radiation energy is often stored in the sheet by being exposed to natural radiation before the sheet is used for recording radiation image information again. Therefore, even in the case where the stimulable phosphor sheet has already been subjected to the erasing process (primary erasing process), the erasing process is generally carried out again (secondary erasing process) immediately before the stimulable phosphor sheet is reused for recording radiation image information.
As has been described in U.S. Pat. No. 4,849,630 for example, the stimulable phosphor sheet is often stored in a light-shielding cassette. The cassette stores only one sheet and usually comprises a casing box having an opening for inserting or taking out the sheet and a lid for opening or closing the opening.
When a radiation image is photographed (recorded) by using such a cassette, the cassette is placed in a position where radiation that has passed through a subject is irradiated, for example. In this manner, the radiation is irradiated on the stimulable phosphor sheet stored in the cassette, and the radiation image is recorded in the sheet.
The cassette after photographing the radiation image is set in a radiation image information reading apparatus, as has been described in U.S. Pat. No. 5,308,994, for example. The stimulable phosphor sheet is taken out from the cassette and subjected to radiation image information reading processing.
Meanwhile, for the stimulable phosphor sheet that has the radiation image recorded therein, information such as a name and a body portion of the subject and a radiation dosage needs to be specified for the subsequent radiation image information reading and sheet management. In many cases, subject information such as the name and gender of the subject and ID (identification) information including photographing information such as the date of photographing and the photographed body portion is registered with a photographing information registration apparatus. The photographing information registration apparatus is placed together with or connected to the radiation image photographing apparatus. The photographing information registration apparatus is connected to the radiation image information reading apparatus in some cases so that a radiation image information reading condition can be determined based on the photographing information.
In the case where the stimulable phosphor sheet is stored in the cassette, the subject information and the photographing information is often represented by a bar code and the bar code is pasted to the cassette.
Meanwhile, the time necessary for the erasing process such as the primary erasing and the secondary erasing is substantially long compared to the time necessary for the radiation image information reading process. This fact has been hampering the processing ability of the radiation image recording/reproducing system using a stimulable phosphor sheet. In consideration of such a situation, a cassette comprising an emitter for the erasing process has been proposed as in U.S. Pat. No. 4,849,630, aiming at an improvement of the erasing process.
Although the cassette having the emitter can achieve a predetermined object, the cassette needs to be brought to a power supply unit for supplying an electric current to the emitter. Furthermore, appropriate control of emission time of the emitter is difficult. With regard to these points, there remained room for improvement.
The present invention has been conceived based on consideration of the above circumstances. An object of the present invention is therefore to obviate the conveyance of a cassette having an erasing ray emitter to a power supply, and to appropriately control an emission time of the emitter.
Another object of the present invention is to provide a radiation image photographing apparatus, a photographing information registration apparatus, and a radiation image information reading apparatus enabling appropriate control of the emission time of the emitter from outside of the cassette.
Still another object of the present invention is to provide a radiation image photographing apparatus and a photographing information registration apparatus not hampering photographing of a radiation image even if the emission time is controlled.
A cassette of the present invention is a cassette for storing a stimulable phosphor sheet having a stimulable phosphor layer formed on a sheet-like substrate and used for recording a radiation image therein, and the cassette comprises:
an emitter for emitting an erasing light to the sheet stored in the cassette;
a power supply for causing the emitter to emit the erasing light; and
a control circuit for controlling a time of emission from the emitter powered by the power supply.
The control circuit controls the emission time based on control information input from outside of the circuit.
More specifically, a circuit for controlling the emission time based on control information output from an apparatus for photographing the radiation image on the stimulable phosphor sheet may be used as the control circuit. Alternatively, a circuit for controlling the emission time based on control information output from an apparatus for registering photographing information regarding the stimulable phosphor sheet, or a circuit for controlling the emission time based on control information output from an apparatus for reading radiation image information from the stimulable phosphor sheet may also be adopted as the control circuit, for example.
In the case where the control circuit for controlling the emission time based on the control information input from the outside of the circuit is used, means for receiving the control information input from the outside is necessary. As such means, a terminal for receiving the control information input from the outside, radio reception means according to a wireless communication standard such as Bluetooth, Wireless 1394, and IEEE 802.11, and infrared reception means according to an infrared communication standard such as IrDA may be used, for example.
As the power supply for causing the emitter to emit the erasing light, a rechargeable secondary battery such as a Li(lithium) -ion battery (especially a Li-ion polymer battery) is preferably used. In this case, it is preferable for the cassette of the present invention to comprise means for said secondary battery to receive a charging electric current supplied from outside of said secondary battery.
It is preferable for the emitter to comprise an organic EL (electroluminescence) material or non-organic EL material.
The emitter is preferably placed facing a surface of the stimulable phosphor sheet on a side of the stimulable phosphor layer. Alternatively, in the case where the cassette of the present invention stores the stimulable phosphor sheet having the stimulable phosphor layer formed on a substrate which allows the erasing light to pass through, the emitter may be placed facing a surface of the sheet on a side of the substrate or facing the sheet on both sides.
As has been described above, the stimulable phosphor sheet stored in the cassette of the present invention has the stimulable phosphor layer formed on the sheet-like substrate. However, in many cases, a protective layer or the like is also used. Therefore, the xe2x80x9csurface of the sheet on the side of the stimulable phosphor layerxe2x80x9d does not necessarily refer to a surface of the stimulable phosphor layer, but refers to a surface of the sheet to which the stimulable phosphor layer is placed closer than the substrate. Likewise, the xe2x80x9csurface of the sheet on the side of the substratexe2x80x9d refers to a surface of the sheet to which the substrate is placed closer than the stimulable phosphor layer.
It is preferable for the cassette of the present invention to comprise display means for indicating that the emission is occurring and/or completed.
Furthermore, it is also preferable for the cassette of the present invention to further comprise time measuring means for measuring a time elapsed since completion of the emission and re-erasing control means for causing the emitter to emit the erasing light again when the elapsed time measured by the time measuring means reaches a predetermined time.
Moreover, it is also preferable for the cassette of the present invention to further comprise warning means for issuing a warning if the emitter is still emitting the erasing light when information indicating that the cassette is set in a photographing stand-by state is input thereto. In this case, the information may be input from the outside of the cassette. Alternatively, the cassette may comprise detection means for inputting the information to the warning means by detecting the stand-by state.
It is also preferable for the cassette of the present invention to further comprise emission stopping means for stopping the emission of the erasing light from the emitter if the emitter is still emitting the erasing light when information indicating that the cassette is in a stand-by state is input thereto. In this case, the information may be input from the outside of the cassette. Alternatively, the cassette may comprise detection means for inputting the information to the emission stopping means by detecting the stand-by state.
Meanwhile, a first radiation image photographing apparatus of the present invention uses the cassette comprising the control circuit for controlling the emission time based on the control information output from the radiation image photographing apparatus. The first radiation image photographing apparatus comprises means for inputting information related to a radiation dosage for the stimulable phosphor sheet as the control information to the control circuit of the cassette.
A second radiation image photographing apparatus of the present invention uses a cassette comprising a warning means for issuing the warning if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette. The second radiation image photographing apparatus comprises detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the warning means of the cassette.
A third radiation image photographing apparatus of the present invention uses a cassette comprising an emission stopping means for stopping the emission from the emitter if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette. The third radiation image photographing apparatus comprises detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the emission stopping means of the cassette.
A first photographing information registration apparatus of the present invention registers the photographing information regarding the cassette (that is, regarding the stimulable phosphor sheet stored therein) comprising the control circuit for controlling the emission time based on the control information output from the first photographing information registration apparatus. The first photographing information registration apparatus comprises means for inputting information related to a radiation dosage for the stimulable phosphor sheet as the control information to the control circuit of the cassette.
A second photographing information registration apparatus of the present invention registers the photographing information regarding the cassette (that is, regarding the stimulable phosphor sheet stored therein) comprising the warning means for issuing the warning if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette. The second photographing information registration apparatus comprises detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the warning means of the cassette.
A third photographing information registration apparatus of the present invention registers the photographing information regarding the cassette (that is, the stimulable phosphor sheet stored therein) comprising the emission stopping means for stopping the emission from the emitter if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette. The third photographing information registration apparatus comprises detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the emission stopping means of the cassette.
A radiation image information reading apparatus of the present invention is an apparatus for reading the radiation image information from the stimulable phosphor sheet stored in the cassette comprising a control circuit for controlling the emission time based on the control information output from the radiation image information reading apparatus. The radiation image information reading apparatus of the present invention comprises means for inputting information related to a dosage of radiation for the stimulable phosphor sheet as the control information to the control circuit of the cassette.
According to the cassette of the present invention, the cassette comprises not only the emitter for irradiating the erasing light to the sheet but also the power supply to cause the emitter to emit the erasing light. Therefore, an erasing process can be carried out on the stimulable phosphor sheet by supplying the electric current from the power supply to the emitter, without bringing the cassette to a power supply unit.
Furthermore, the cassette of the present invention comprises the control circuit for controlling the emission time of the emitter powered by the power supply. Therefore, the emission time can be controlled appropriately.
Each of the first radiation image photographing apparatus, the first photographing information registration apparatus and the radiation image information reading apparatus of the present invention using the cassette comprises the means for inputting the information related to the radiation dosage for the stimulable phosphor sheet as the control information to the control circuit of the cassette. Therefore, the emission time of the emitter of the cassette can be controlled appropriately from the outside of the cassette.
In the case where a rechargeable secondary battery is used as the power supply for causing the emitter to emit the erasing light, the power supply can be used repeatedly by recharging the battery, which is economical. Especially, in the case where the Li-ion polymer battery is used as the secondary battery, this battery can be formed extremely thin, as thin as 2xcx9c3 mm. Therefore, the cassette can also be thin and light. Furthermore, since the Li-ion polymer battery can also be formed to have a large area, the battery can be as large as up to an area of the stimulable phosphor sheet. As a result, the amount of the erasing light can be large. Furthermore, since the emission time can be longer, the interval between recharging operations can be longer.
Meanwhile, in the case where a non-organic or organic EL material is used for the emitter, the material can be shaped extremely thin. Therefore, the cassette can also be thin. Furthermore, the non-organic or organic EL material can be used without a driving circuit or a wire therefor. Therefore, even in the case where the radiation image is photographed in a state where the emitter comprising the non-organic or organic EL material is situated between the stimulable phosphor sheet and a radiation source, the photography of a driving circuit or a wire in the radiation image can be prevented.
If the emitter is placed facing the surface of the sheet on the stimulable phosphor layer side, the erasing light can be efficiently irradiated on the stimulable phosphor layer even if the erasing light cannot pass through the substrate of the sheet.
Meanwhile, if the cassette of the present invention stores the stimulable phosphor sheet having the stimulable phosphor layer formed on a substrate that allows the erasing light to pass through, the erasing light can be irradiated on the stimulable phosphor layer through the substrate even if the emitter is placed facing the surface of the sheet on the substrate side. In this case, if the emitter is also placed facing the surface of the sheet on the stimulable phosphor layer side, the erasing light can be irradiated on the stimulable phosphor layer from both sides. In this manner, the erasing process can be carried out efficiently in a short time.
If the cassette of the present invention comprises a display means for indicating that the emission is going on and/or completed, whether or not the erasing process on the stimulable phosphor sheet in the cassette has been completed can be judged easily. In this manner, the stimulable phosphor sheet can be prevented from being reused for photographing another radiation image without completion of the erasing process thereon.
If the cassette of the present invention comprises a time measuring means for measuring the time elapsed after completion of the emission and the re-erasing control means for causing the emitter to emit the erasing light again when the elapsed time measured by the time measuring means reaches the predetermined time, energy of natural radiation or the like can be released even if the energy is stored in the sheet which has been subjected to the erasing process. Therefore, the stimulable phosphor sheet can be used for photographing another radiation image in a state where a level of residual radiation energy is extremely low.
If the cassette of the present invention comprises a warning means for issuing a warning if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette, the stimulable phosphor sheet can be prevented from being reused for photographing another radiation image in a state where the erasing process is incomplete, that is, in a state where the level of the residual radiation energy is still high.
Each of the second radiation image photographing apparatus and the second photographing information registration apparatus of the present invention using the cassette comprises a detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the warning means of the cassette. Therefore, a stimulable phosphor sheet whose residual radiation energy level is high can be prevented from being reused in the apparatus.
If the cassette of the present invention comprises an emission stopping means for stopping the emission from the emitter if the emitter is still emitting the erasing light when the information indicating the stand-by state of the cassette is input to the cassette, photographing of a radiation image can be prevented from being hampered in an emergency state, in which photography must be performed, due to the emission time control.
Each of the third radiation image photographing apparatus and the third photographing information registration apparatus of the present invention using the cassette comprises a detection means for detecting the stand-by state of the cassette and for inputting the information indicating the stand-by state to the emission stopping means of the cassette. Therefore, by use of the apparatus, the emission time control does not hamper radiation image photographing.